The present invention relates to an interface module apparatus for connection to an electrical machine, which has a bearing, and for outputting a remaining life of the bearing. The present invention also relates to a corresponding electrical machine having this interface module apparatus.
Bearing wear or bearing fatigue resulting from overloading leads to failure of a corresponding bearing of a motor, and thus to failure of the motor. The bearing wear resulting from a decrease in the lubrication characteristics of the grease is dependent on the load history on the bearing, in particular the bearing temperature and rotation speeds, and is responsible for the majority of bearing failures of motors. Bearing fatigue is dependent in particular on the load on the bearing from lateral force, oscillations or vibration that are introduced, and rotation speeds.
Frequently, only general, computationally determined bearing replacement cycles based on trials are recommended for motors. In general, individual wear and fatigue states are ignored.
Monitoring of the life of and the load on bearings is known from the document DE 199 37 203 A1. In this case, a system senses rolling element loads in real time in a rolling element bearing. A multiplicity of sensors are arranged around one of the inner roller paths and the outer roller paths of the bearings, in order to output sensor data corresponding to the loads that are found. A control unit predicts the bearing life from the sensor data, and determines a load range of the bearing in real time from the sensor data. The sensor data is extracted cyclically, and peaks and troughs are extracted from the sensor data, in order to determine rolling element loads and a measured bearing speed.
Furthermore, patent specification DE 100 39 015 C1 discloses a method and a device for monitoring the rotating bearings of extrusion supporting rollers. In order to determine the remaining life of roller bearings and journal bearings, the mechanical and thermal loads (all loads) on one or more rotating bearings are measured and stored continuously. The digital measurement results are processed in an evaluation and storage unit, and a ratio is calculated from all the loads and the limit load capacity of the respective rotating bearing, from the total number of all loads.
The document DE 102 57 793 A1 discloses a model-based life monitor. In this case, the system loads are determined from the existing vehicle sensor system, and the sensor signals are processed to form load time profiles. Local component loads are determined from the system model and the load time profiles. Finally, the remaining life of the components contained in the system model is calculated by means of a serviceability analysis from the accumulated component damage.
Furthermore, the document U.S. Pat. No. 6,529,135 B1 discloses an integrated electric motor monitor. In this case, the operating conditions of the electric motor are monitored and appropriate prediction information is stored in a storage device. In this case, inter alia, the temperature, the motor rotation speed and the winding temperature are monitored.
Determination of the remaining life using the methods mentioned above generally requires extensive measurement and computation apparatus.